Exterior surface of a front bumper for an automobile



FIG. 1 is a perspective view from above and in front of an exterior surface of a front bumper for an automobile according to my novel design;

FIG. 2 is a front view of an exterior surface of a front bumper for an automobile according to my novel design; and,

FIG. 3 is a left side view of an exterior surface of a front bumper for an automobile according to my novel design.

The broken lines are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a exterior surface of a front bumper for an automobile, as shown and described. 